The present invention relates to a diaphragm-type air pump, and more particularly to a diaphragm-type air pump capable of fully utilizing magnetomotive force of an electromagnet, for example, reducing leakage magnetic flux or effectively utilizing gap magnetic flux between main poles and side poles, whereby remarkably improving pump capacity, and lightening and miniaturizing pumps.
Hithereto, diaphragm-type air pumps have been used mainly in supplying oxygen to water tanks for pisciculture or domestic purifying chamber, or in sampling inspection gas for the monitoring of environmental pollution.
An electromagnet consisting of a core 30 comprising an E-shaped laminated iron plate shown in FIG. 15 and coils (not shown) wound around the core 30 has been used in the above-mentioned conventional diaphragm-type air pump. In FIG. 15, numerals 31 and 32 are a main pole and a side pole, respectively.
When increasing the number of turns of coils to increase magnetic flux and power of a pump in the electromagnet having a structure as described above, there is a restriction on the size of a "vacant space" for coils (refer to a in FIG. 15) so that the number of turns of coils is limited. Therefore, it has been proposed to increase the size of a vacant space for coils, or to increase the depth of the electromagnet (refer to b in FIG. 15) In either case, however, there are drawbacks as stated below so that the pump capacity cannot be improved That is, when increasing the size of a vacant space for coils, the increase of gap magnetic flux or passing magnetic flux is limited because of the increase of a gap or distance between the main pole and side pole. Further, the width of a permanent magnet overlapping the main pole and side pole is enlarged and accordingly the weight of the magnet is increased, so that the proper resonant frequency of a vibration system is lowered. As a result the pump capacity is lowered contrary to expectations. On the other hand, when increasing the width of the electromagnet, leakage magnetic flux (.phi..sub.1) is increased (refer to FIG. 16) due to the increase of permeance coefficient. Moreover, effective magnetic flux (.phi..sub.2) is not equally increased. As a result the pump capacity cannot be improved as is expected, since the magnetic flux is not efficiently utilized
It is an object of the present invention to solve the above-mentioned drawbacks and to provide a diaphragm-type air pump capable of effectively utilizing magnetomotive force of the electromagnet, whereby remarkably improving pump capacity, and lightening and miniaturizing pumps.